[77 TRASHCAN]

Originally Posted by mchell

Original poster....I do apologize for hijacking your thread

Cliff,
Thanks .....appreciate your comments

Snapped my N crank in half recently and looking to shore up some areas ...

I rarely see hijacks, here, unless it's me, of course. I'm still looking to learn, every day. Your questions always propel the process!!
Thanks
Jeff

[adynes]

Originally Posted by chiphead

Why not just slow down the timing curve to come all-in by 3000-3500 and not 2500? See what that does. I thought the modern chambers and high compression don't need a quick curve?

Agree. Would be the first thing I would try before buying/changing any parts. although I don't think he has very modern chambers (old style E heads?).

34* in by 2500 is a horrible timing curve. If I were guessing a timing curve for a computer controlled spark map, I would start with something like:
34* @ peak hp (5000?)
30* @ peak tq (3500?)
15* base
Blend to a gradual S curve, and then fine tune from there.

To get that with a mechanical distributor, your going to need much stiffer springs, probably limit mech. advance travel (from the low end, not the high end, to keep the curve shape the center plate creates) to allow a bump in base timing. And of course experiment with limiting the vac adv. can travel for part throttle driving.

[Cliff R]

"Cliff,
Thanks .....appreciate your comments

Snapped my N crank in half recently and looking to shore up some areas ..."

Yikes, don't see that all to often but it's never pretty when it happens!.......Cliff

[mchell]

Originally Posted by Cliff R

"Cliff,
Thanks .....appreciate your comments

Snapped my N crank in half recently and looking to shore up some areas ..."

Yikes, don't see that all to often but it's never pretty when it happens!.......Cliff

Nope, not fun hearing that mess......funny thing is I personally know 2 others that have had this happen(in my small world)......both large journal 455 making 500- 600hp

Back to the drawing board I guess.....

[Johnny99]

Wow. I go away for a minute and now it's all this.

The wife saw how frustrated I'd become and suggested I take a few days off from the car.

I'll get the compression test done tomorrow. I've also got a set of colder plugs (BKR7E/4644) to try. I'll check out the timing curve at the same time.

The vacuum advance isn't hooked up and there are factory springs in the distributor. Can you get heavier springs? I ordered a Moroso set to see if they offer any more resistance. I'm not sure how else to slow the curve down Though I'm going to bring the initial back down again to test.

The only reason I haven't purchased the wideband gauge yet is I didn't get bungs installed when I had the exhaust done. I should have. I'm going to call and see what's involved in adding them. I'm thinking that in the collectors would be the way to go

Consensus is pretty much it's the wrong cam so that's probably the case. I am going to test everything suggested here first though before pulling the cam again. Thanks

[72LuxuryLeMansLa.]

Originally Posted by Johnny99

Wow. I go away for a minute and now it's all this.

The wife saw how frustrated I'd become and suggested I take a few days off from the car.

I'll get the compression test done tomorrow. I've also got a set of colder plugs (BKR7E/4644) to try. I'll check out the timing curve at the same time.

The vacuum advance isn't hooked up and there are factory springs in the distributor. Can you get heavier springs? I ordered a Moroso set to see if they offer any more resistance. I'm not sure how else to slow the curve down Though I'm going to bring the initial back down again to test.

The only reason I haven't purchased the wideband gauge yet is I didn't get bungs installed when I had the exhaust done. I should have. I'm going to call and see what's involved in adding them. I'm thinking that in the collectors would be the way to go

Consensus is pretty much it's the wrong cam so that's probably the case. I am going to test everything suggested here first though before pulling the cam again. Thanks

http://www.arkansaspontiacs.org/tech...s/recurve.html

[moontower69]

If its pinging at 2500 and above and distributor timing/curve doesn't help, then CLIFF is right, it's the camshaft.

EITHER (1) the cam is too small or (2) cam is not installed correctly and the cam timing needs to be retarded. Possible the timing chain is mismarked or defective (seen that before).

Just my 2 cents.

[pastry_chef]

Yes, the cam is small and not ideal.

Yet, in the last year there have been two different members with this issue. Both swapped to a larger cam/112 LSA as the board prescribed and the issues persisted.
Then it was,, your compression is too high, or your gas is crap..

[chiphead]

Then I would suspect crappy quench, oil contamination of intake charge, or high intake air temp.

[moontower69]

You're about 10.5:1 with those 87cc Edelbrock Aluminum heads (maybe 10.7 if you're zero decked on the chamber) and that's just not problematic for aluminum heads.

Keep in mind it's two unknowns: You didn't install the cam yourself (and degree it) and you don't know if the timing chain markings are a little off. Personally, I'd retard it 4 - 6 degrees, if its still pinging then you know the cam is FUBAR for that build. It will only take you a few hours to get timing cover off, put a torch on the sprocket and reset that timing chain 4-6 degrees retarded.

[glhs#116]

I'm following this thread with interest. I've got my combo running quite well but it's weird settings:
8 initial
vac limited to 12 degrees total
vac spring stiff so only adding 10 degrees at idle (18 at idle)
mechanical advance with heaviest springs, light weights, limited to 10 degrees total with hard stops (total 18 full mechanical advance)
I'm on NGK 8 heat range which is colder than most run on these heads. It will ping with even one more degree but with these settings it drives nicely and doesn't ping.
Crower 60919. Edelbrock round port 87cc, 455 +.030 block, 10.2:1
I don't have access to high octane fuel here but what I have should equate to around a US 89 octane or so (95 RON octane)..

I have some 9 and 10 range plugs. Haven't had time to try them yet though..

Sam

[Jay S]

It will be very helpful to compare notes between Sam’s combo and this thread. Especially now that it appears your both using the same brand of spark plugs. NGK. Plus both of you appear to have similar goals for how your using your cars. My guess is a 9YC is between a 5 and 6 NGK. Might be different in the Pontiac though, only way to compare them really is to try it.

The Summit 2802 comes with 5 degrees of advance. Ussually they are ground on a 109 ICL. FWIW, I think probably the most you can or should retard that cams is 3 or 112 ICL. It’s 10 degree spread with more duration on the exhuast starts to get the exhuast opening events ahead of the intake after that. After that point I think it probably starts to have a lot of reversion and also starts putting extra heat into the air charge. Retarding it and running a 1.65 on the intake and a 1.5 on the exh might make the window a little bigger. It seems to be right in that area were it has enough overlap to cause problems when run retarded much. My opinion, I have done about 20 or so of the summit type 2800,2801,2802 grinds.

That 2802 with a 1.65 rocker gets the specs close to what I have seen the crower 60919 run with 1.5s. At least the 60919s have have done in recent years. The last 60919 I did spec’d out on the small side. I think I had 2 60919s 283- 285 @ .006 and 227-229 @.050. IRC, @ .006 the 2802 runs close to those seat timings just has less .050 durations, but a set of 1.65s would get the 2802 to act similar to a cam in that 284 .006, 228@.050. Which is knocking on the door of a crower 60243 and the 60919s that seemed to be ground on the short side. The actual ram air 4 grind were low 290s on the .006 specs. Majority of engines that are just running regular lifters the 60919 is a better cam IMO than the 041 melling spec-8, unless your above 10 scr, we switch to the melling from there up. Theoretically off the specs the crower should be as big, some may be, the gentlemen earlier complaining about the 60919s street manors sounds like more what I expect from the grinds the are closer to a actual ra 4 cam. To me if you end up switching cams to knock the compression down the next step up for this engine cam wise is a melling spc-8, I would skip past the 60919.

[455TA]

Just FWIW. I have virtually the same shortblock and heads. TRW flat tops with 87cc E heads. I run a xr288 Hyd Roller - 236/242@050, 600/620 lift with Harland Sharp 1.65 rockers. 170 cranking compression. I can run my engine on 89 octane and run 11.17@120 in the 1/4 with a 3400 stall, 3.42 gears, at 3800 lbs with no pinging. When I calculated out my compression ratio, it came out to 9.57:1 with those heads and TRW's. Thats without it zero decked, and my chambers are really 89cc.
There must be more going on with your setup. Not enough cam, heads possibly 72 cc's vs 87, cam timing off, etc.

[pastry_chef]

Originally Posted by 455TA

87cc E heads.

Any port work?

[TAQuest]

Definitely 'something else' going on if the compression is only 160 like reported.

It would be hard to make a serious 'ping' event at that compression with 93 octane with two bottles of octane booster.

It's the gorilla in the room. I have my theory but it would depend on a confirmation of the compression test.

[455TA]

Originally Posted by pastry_chef

Any port work?

307 cfm at .700 lift - just minor clean up

[Cliff R]

My engine cranks 198-200 psi in every hole, 11.3 to 1 true static compression ratio, and fine on pump gas now for over 10 years. It will even manage 87 octane, but every once in a while will "run-on" if it's 9 million degrees outside and fully heat soaked, so I keep 92-93 in it to give me a "warm and fuzzy".

Cranking pressure is NOT the tell tale indicator for octane requirements. There is a LOT more going on in one of these engines.

If you follow the "recipe" for success, and come up short, almost every single time it will be that something was left out, not done to spec, or missed. I've been building these engines now close to 4 decades, but didn't really get good at it till the last 20 years. I also have very close control of timing and fuel curves. When I opened up the shop couple of years ago on Saturday mornings by appointment I've had scores of troubled vehicles brought here for custom tuning.

Rest assured most if no all of them had been well "worked over" by the owner, engine builder, tuner, and every relative/close neighbor/drinking buddy the owner knew tall enough to see over the fenders and hold a wrench! I've been able to fix just about every single one, even if I had to "crutch" things someplace because they made a piss-poor cam selection (for example).

Recently had a guy come all the way from Canada, over 1000 miles and pay us a visit. He was a good wrench and very well set up engine and drivetrain combo, but it wasn't fully up to par. I spend a couple of hours on it, mostly carb work and he left here the happiest guy in Canada that day. He had already purchased the parts to do the work himself, and my Q-jet book, but made a few minor errors, or missed a few things in half a dozen or so areas, so not getting anywhere near full potential from the combination. That's just the way it is with this stuff, and why some folks have zero issues, and others trying to do the same thing aren't getting away with it......FWIW......Cliff

[TAQuest]

If you can't make it go away raising the octane and retarding the timing then it's not detonation, it's another rattle coming from the engine.

[Johnny99]

I'm thinking that TAQuest may be right though of course I hope not. Here is a video of the issue https://youtu.be/aUujtuc-_jg.

Cranking compression I get this

1. 150
2. 160
3. 160
4. 160
5. 160
6. 150
7. 160
8. 160

Temperature driving around at about 30 mph is 180. In garage doing the timing check about 200. It's' about 75 out today. Colder BKR7E plugs installed

The distributor is a stock cast iron unit out of a 66 GTO with stock springs and weights. I did have to replace the can on it and it's got a B1 on it now that I limited to 14 total but the vac advance is not hooked up right now.

To test the max advance I pulled 1 spring off of the weights and total mechanical advance was right around 24 bring timing total to 30 though I never hit that with the 2 springs installed. I suppose ultimately this distributor will need lighter springs but that is the least of my issues

• 500 (idle in park with no vac adv) 6 btc
• 1000 10 btc
• 1500 14 btc
• 2000 15 btc
• 2500 15 btc
• 3000 18 btc

I drained the tank to about 5 gallons and added a can of VP Octanium. There was no access to racing fuel yesterday. Based on the above I would find it hard to believe the high octane would make a difference though since the total advance in the car now seems pretty mild .

[pastry_chef]

I highly recommend
https://www.summitracing.com/int/par...0300/overview/